The carpet industry in the United States is an estimated fourteen billion dollar a year industry. It is estimated that over 1.3 billion square yards of carpeting are produced and sold annually. Approximately one-half of the sales of this carpeting per year is in the replacement market, for replacement of old or worn carpeting, primarily in the area of institutional use. Statistics show that approximately 2.4 billion pounds of polymer face fibers, such as nylon, polyester, or polypropylene materials, are used in the manufacturing of carpet in the United States every year.
However, with this large scale production of new carpet and the replacement of old or worn carpeting comes a large amount of waste. Carpet waste is estimated at over one billion pounds per year. Most of this waste carpet material is disposed of in landfills throughout the United States. Existing landfills are rapidly becoming full, new landfill space is at a premium, and the cost of disposal of waste materials is rising rapidly as a result. Additionally, the polymer fibers currently being used in carpeting and discarded as waste present a serious environmental concern since such polymer materials do not readily degrade or break down. Thus, conventional disposal of such materials is simply a net loss.
There are great potential savings both financially and environmentally to be realized from the recovery and recycling of waste polymer fibers used in the production of carpeting. Recycling would save millions of dollars per year by eliminating the cost of waste management and disposal of carpeting and waste materials from the manufacture of carpeting in landfills. Additionally, use of recycled materials will result in lower cost for the manufacture of the carpeting, will greatly reduce the use of virgin raw materials, and will significantly reduce or eliminate the environmental impact of the disposal of such polymeric materials.
Recently, extraction methods have been developed for the separation of materials, such as polymeric materials from multi-component systems and for the removal of impurities from polymeric plastic materials by introducing an extraction gas in a supercritical state to dissolve and or remove the specific materials or impurities. For example, U.S. Pat. No. 4,714,526 of Pennisi et al and U.S. Pat. No. 5,080,845 of Hermann et al show methods of supercritical fluid extraction for extracting pure components or impurities from multi-component mixtures of materials. The components are dissolved in a supercritical fluid to form a solution. The solution is then drawn off, removing the desired component from the remaining component mixture. Such methods, as disclosed in Pennisi et al have not been applied to the recovery and recycling of polymeric materials such as carpeting materials. Indeed, the method disclosed by Pennisi et al appears to be ill suited for use in recycling and recovering polymeric materials.
Pennisi et al discloses an extraction method wherein all of the components of the mixture are dissolved into the supercritical solution at the same time. Thus, Pennisi et al requires that the temperature of the supercritical solution be high enough for all of the components to be dissolved simultaneously. In the case of the recovery of polymers from carpets, it is not practical or desirable to subject all of the components of the carpeting material to the highest temperature necessary to solubilize the component with the highest melting point. Such high temperatures can cause thermal damage to polymer molecules, for example by converting polymers to monomers, thereby rendering the polymeric material unfit for recycling and reuse in the desired manner of the present invention.
Accordingly, all the polymeric materials should be recovered at their lowest possible temperature in order to avoid such thermal damage. Most of the different polymeric materials used in the makeup of carpeting have different temperatures at which these polymeric materials dissolve in supercritical fluids. For example, to recover polyester, the temperature of the supercritical solution must be about 100.degree. C. higher than that required for dissolving polypropylene. Accordingly, the extraction method of using a supercritical fluid at extremely high temperatures to dissolve out and extract a component from a multi-component material as taught by Pennisi et al would be ill suited for use in the recovery and recycling of polymeric materials from carpeting or other structures.
Therefore, it is seen that a need exists for a method of recovering and recycling polymeric material from waste carpeting, carpeting materials, and like structures that enables a substantially complete recovery of all of the different polymeric materials without risking damage to the polymers and rendering them unfit for reuse in the production of new carpeting or other products made from such materials.